For high integration of semiconductor devices, through-holes are important to be formed well. Those through-holes are formed to connect multilayered conductive layers on different levels.
In fabrication of a conventional semiconductor device, a barrier layer with low reflection rate is formed on a conductive layer, an insulation layer is formed on the barrier layer, and then the insulation layer is etched to form through-holes. In this processing, the barrier layer is not etched. Usually, aluminum and its alloy is used as the conductive layer, however, aluminum has a high reflection rate which is bad for lithography processing, that is, aluminum layer makes resolution of lithography processing lower and patterning process worse. That is why the barrier layer which has a low reflection rate, such as TiN having a thickness of hundreds .ANG., is necessary to be formed on the aluminum layer. According to this kind of fabrication processing, the barrier layer makes conduction characteristic between the through-holes and the conductive layer low, because the barrier layer usually has a high insulation rate. On the other hand, if the barrier layer is also etched in the formation of through-holes, pieces of the conductive layer (deposits) are stuck on the inside surface of the through-holes, and therefore, electrical characteristics and quality of the through-holes become worse.
In fabrication of another conventional semiconductor device, a barrier layer with low reflection rate is formed on a conductive layer, a cap-layer such as tungsten (W) is formed on the barrier layer, an insulation layer is formed on the cap-layer, and then the insulation layer and the cap layer are etched to form through-holes. This conventional technique has the same problems as the above mentioned another conventional technique.